The light-emitting diode is widely applied in the domestic electronic appliances, the indicator for the instrument, light sources for the optoelectronic products, and the optoelectronic communication due to its low electricity consumption, low heat dissipation, long operating life-time, strike-proof, small volume, rapid response speed. The light-emitting diode also has good optoelectronic characteristics such as stable wavelength of the color light.
In a conventional light-emitting diode structure, a contact layer is normally formed to provide a lower contact resistance between an electrode and a semiconductor structure below the electrode. When an electrode is formed on the contact layer, the ohmic contact is formed as a result of a lower contact resistance of the junction between the electrode and the contact layer. The contact layer has a higher doped impurity concentration than those of other semiconductor epitaxy layers, such as a cladding layer. When the ohmic contact is formed between the contact layer and the electrode, the light-emitting diode has lower forward voltage and higher light-emitting efficiency. The light-emitting efficiency of the light-emitting diode is the product of the internal quantum efficiency and the light extraction efficiency. In general, the internal quantum efficiency related to the property of the material and the quality of the epitaxy layers. The light extraction efficiency related to the index of refraction of the material and the flatness of the surface. To increase the light extraction efficiency, a contact layer having roughing surface can be formed directly by the epitaxy technology. It can reduce the probability of the total reflection of the light emitted from the active layer and increase more than 30% of the light extraction efficiency. A current spreading layer is formed on the contact layer to increase the effect of the current spreading, but the effect of the current spreading can be decreased when the surface of the current spreading layer is not flat.
The FIG. 5 illustrates a known light-emitting apparatus showing a light-emitting apparatus 600 including at least a submount 60 with a solder 62 and an electrical connecting structure 64 on the submount 60. The light-emitting device 400 is adhered on the submount 60 by the solder 62, and the first electrode 56 and the second electrode 66 of the light-emitting device 400 are electrically connected with an electrical connecting structure 64 and the submount 60 respectively. Except for the submount 60, the package carrier can also be a lead frame or mounting carrier convenient for the circuit design of the light-emitting apparatus and the high heat dispersion.